01-08-2010 02:41 AM - edited 03-06-2019 09:12 AM
Hi
Suppose if a new link is added in an existing STP switched network. Does TCN is generated? If not, then how all switches learn the new link. Or even the same switch, which might have a different root port, but after adding the new link, it could be the lowest cost to the root. So I wanted to know how the new link added is known to the same switch and other switches.
Regards
Mohamed.
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01-08-2010 02:56 AM
Hi
Suppose if a new link is added in an existing STP switched network. Does TCN is generated? If not, then how all switches learn the new link. Or even the same switch, which might have a different root port, but after adding the new link, it could be the lowest cost to the root. So I wanted to know how the new link added is known to the same switch and other switches.
Regards
Mohamed.
Mohamed
When you say new link do you mean a new switch ? A TCN can be generated simply by a host going up and down on a port if portfast is not enabled.
However if a switch is added that switch will generate BPDUs which will be received by the other switches. This is how the other switches are aware of a new switch being added.
Jon
01-08-2010 04:32 AM
Hello Mohamed,
the TCN is generated and it is indeed the trigger for a new STP calculation that involves all the switches.
so a new better root port can be chosen following your example. in steady state only designated ports transmit BPDUs
STP duty is to handle link redundancy at layer2 by building and mantaining a loop free topology.
it is a dynamic process and in this it is similar to a routing protocol
to be noted that STP is not interested in advertising MAC addresses or links but root bridge reachability
Hope to help
Giuseppe
01-08-2010 02:56 AM
Hi
Suppose if a new link is added in an existing STP switched network. Does TCN is generated? If not, then how all switches learn the new link. Or even the same switch, which might have a different root port, but after adding the new link, it could be the lowest cost to the root. So I wanted to know how the new link added is known to the same switch and other switches.
Regards
Mohamed.
Mohamed
When you say new link do you mean a new switch ? A TCN can be generated simply by a host going up and down on a port if portfast is not enabled.
However if a switch is added that switch will generate BPDUs which will be received by the other switches. This is how the other switches are aware of a new switch being added.
Jon
01-08-2010 04:32 AM
Hello Mohamed,
the TCN is generated and it is indeed the trigger for a new STP calculation that involves all the switches.
so a new better root port can be chosen following your example. in steady state only designated ports transmit BPDUs
STP duty is to handle link redundancy at layer2 by building and mantaining a loop free topology.
it is a dynamic process and in this it is similar to a routing protocol
to be noted that STP is not interested in advertising MAC addresses or links but root bridge reachability
Hope to help
Giuseppe
01-12-2010 01:37 AM
Hi Jon and Giuseppe
Thanks for your reply.
Regards
Mohamed.
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